Incumbent Democrat Mike Thompson leads the June 2, 2026 top-two primary for California's 4th Congressional District, a D+17 seat rated Solid Democratic by forecasters like Cook Political Report, buoyed by Democratic Party of California endorsement, superior cash-on-hand exceeding $2.5 million as of late March, and a long record on regional issues like wildfire relief and the wine industry. Progressive challenger Eric Jones, with comparable fundraising over $3 million but rejecting corporate PACs, poses the main intra-party threat via digital outreach targeting younger voters. A fragmented Republican field including Mandy Ghusar and Raymond Riehle trails far in funds, unlikely to advance amid the district's partisan lean; no polls available, but split GOP votes could send both Democrats to the November general. No major developments since March filing deadline.